Electric blanket



H. F. SMITH ELECTRIC BLANKET Jam. 9, 1951 2 Sheets-Sheet 1 Filed Dec. 19, 1947 H. F. SMITH ELECTRIC BLANKET Jan. 9, 1951 2 Sheets-Sheet 2 Filed Dec. 19, 1947 INVENTOR Wilma,

BY 7 WMWv-Adon ATTORNEYS Patented Jan. 9, 1951 ELECTRIC BLANKET Harold F. Smith, Cincinnati, Ohio, assignor to Institu um .Divi Thomae Foundation, Cincinnati, Ohio, a corporation of Ohio Application December 19, 1947, Serial No. 792,737

.5 Claims.

This invention relates. to electric blankets of the type having enclosed wires forming an electric heating circuit and a thermostatic control unit for controlling the amount of current flow- :ing in the heating circuit, and more particularly to the manner in which such a unit is combined with and attached to the blanket.

Within recent years electric blankets have gone into extensive use and various types have appeared on the market. The heating circuit is formed by conductors enclosed within the blanket fabric so that they are hidden from view and arranged over the area of the blanket according to a predetermined wiring pattern so as to obtain the desired heat distribution. The position of these conductors within the blanket can be maintained in various ways as by weaving the blanket fabric around the conductors or by the use of two plies of blanket fabric stitched together around or between the conductors, etc. Another very advantageous method of maintaining the desired wiring pattern is that disclosed in the copending application of Harold F. Smith, Serial No. 792,736, filed December 19, 1947, now abandoned, wherein the plies are adheslvely bonded to hold the conductors in place between them. The current flowing in the heating circuit is controlled by a suitable thermostatic con- -trol unit which can be adjusted manually to maintain the current and consequently the heat output at desired approximately constant levels.

The thermostatic control units are of various shapes, sizes and types and heretofore the practice has been to keep such units separate from the blankets and to connect them to the blanket heating circuits by flexible cords or the l ke. It is an object of the present invention to eliminate the connecting cord and the separate control unit by combining such a unit structurally and physically with the blanket itself.

Another obiect of the invention is to provide novel means for housing such a unit as part of the blanket itself in such a way that the manually settable control is always conveniently at hand for the user.

.A further object is to provide such means in a form whereby the unit is securely held .and retained in the blanket but can be disconnected and removed quickly and easily whenever desired.

To the above ends a pocket structure of suitable size and shape to receive and hold the thermostatic control unit is built into the blanket as an integral part thereof. Preferably the unit comprises a flat relatively thin casing which can be held in the pocket with its large dimensions 2 parallel to the plane of the blanket in order to minimize bulging of the blanket. The casing is inserted into its pocket through a suitable opening or mouth which is thereafter closed and fastened around the casing to retain the unit, but the manually settable control member of the unit protrudes through an opening to the outside .of the blanket where it is accessible to the user. Leads from the heating circuit are enclosed within the blanket fabric and extend therefrom directly into the pocket without external exposure, terminating in a suitable connecting member adapted to be connected detachabl to the control unit. Thus the connection of the unit to the circuit is protected against accidental disconnection, .and when the mouth of the pocket is opened and the unit is disconnected and removed, the connecting member is retained in the pocket where .it is always available for quick and easy reconnection of the unit to the circuit.

The pocket structure may have any suitable location and may be incorporated in or attached to the blanket in any suitable way. However, it is desirable to locate the pocket at a point such that the control member can be reached easily and also to insert the unit between two plies of blanket fabric so that such fabric surrounds and encloses theunit' and is continuous or substantially so on both sides of the blanket. Inasmuch as the blanket fabric itself is not adapted to withstand wear over long periods of use, the pocket should be made of some strong, heavy fabric such as canvas. As stated above, such a pocket can be attached to the blanket in any suitable way, as by sewing or stitching or other suitable means, but is preferably inserted between two blanket plies which are secured to the walls of the pocket closely adjacent its mouth, so that the pocket closing means can be firmly secured to the strong fabric of the pocket and may serve to close simultaneously the mouth of the pocket and the opening in the blanket through which the pocket is inserted between the plies.

One embodiment of the invention has been il-. lustrated in the accompanying drawings but it is to be expressly understood that said drawings are for purposes of illustration only and are not to be taken as a definition of the limits of the invention, reference being had to the appended claims for this purpose.

In the drawings,

Fig. l is a perspective view of one embodiment of the invention which comprises a pocket of of flat thin dimensions.

-. the strip at 25.

3 canvas or the like inserted between two plies oi blanket fabric;

Fig. 2 is a side view of the embodiment of Fig. 1, with the outer ply of blanket fabric removed and the pocket shown in section;

Fig. 3 illustrates a suitable thermostatic control unit; and

Fig. 4 is an end view of the embodiment shown in Figs. 1 and 2, both the blanket fabric and pocket fabric being shown in section.

It will be evident that the thermostatic control unit may be of various types as regards its structure and operation, such details not being a part of the present invention. For reasons stated above, however, the unit should preferably be flat and thin in external shape with its manual control member projecting from the casing at a point which will depend on the location and arrangement of the pocket and the opening through which said member protrudes. For purposes of example, the drawings show the pocket formed in one edge of the blanket with the control member projecting beyond said edge, and Fig. 3 illustrates a thermostatic control unit suitable for use in this location.

The casing I of the unit may be of any suitable material such as metal or molded plastic, etc., and is generally rectangular in shape and For example, the casing I may comprise one side wall with the surrounding edge walls of the unit integral therewith. A suitable mounting block 2 at one corner of the unit carries external terminals 3 and 4 whereby the unit can be connected detachably to the heating circuit as described hereinafter. Spacer bushings 5 are located at various points and provided with screw-holes 6 whereby the casing can be completed by a cover plate I secured to the part I by means of screws 8.

A manual control member 9 and an associated indicating dial ID project from one edge of the casing so that when the casing is inserted be "tween the plies at the edge of the blanket as shown in Fig. 1, the control member and dial protrude from the pocket and beyond the blanket edge. In view of the thinness of the casing, it is desirable to make the indicating dial iii of oval shape. a

The details of construction and operation of the thermostatic control means within the easing are not pertinent to the present invention, but a suitable example is illustrated in Fig. 3. A condenser H is bridged across the terminals 3 and 4 by means of the condenser leads l2 and I3 respectively, this condenser serving to suppress arcs, prevent radio interference, etc. A wire It leads from the terminal 3 to an insulated tube i5 held in place by a double clip 16 and containing an electric heating unit. A wire ll leads from this heating unit around the casing to a bimetallic contact strip l8 carrying a contact IS, the wire ll being held on strip 18 by a clip 20 and the end of the wire being riveted to The bimetal strip i8 is mounted by means of rivets 22 on an insulation spacer 23. Contact i9 is adapted to engage a contact 2% carried on one end of a flexible arm 25 the other end of which is interposed between leaf springs 26, the assembly of arm 25 and springs 26 being mounted between the insulation spacer 23 referred to above and an insulating strip 21. The end of the arm 25 is connected at 28 to a wire 29 leading to the terminal 4. With this construction it will be seen that current flows through the unit when the contacts l9 and 24 are engaged but is interrupted when these contacts are disengaged.

The position of the arm 25 and its contact 24 is determined by the setting of the manual control member 9 in the following manner. A shaft 30, suitably connected at one end to the control knob 9 as by means of a pin 3!, extends into the casing and carries at its inner end a button 32 movable through a boss 33 on the insulating strip 21 and engaging the assembly of springs 26 and arm 25. The shaft 30 turns in a bearing 34 carried by a mounting bracket 35 and provided with a helical cam surface 35 engaged by a pin 31 on the shaft. The pin is maintained in engagement with the cam surface by the springs 26, and as the control knob 9 and shaft 39 are rotated, the pin rides on the cam surface and the shaft and button 32 are thereby moved downwardly from the position shown in Fig. 3 to deflect the springs 26 and arm 25 and adjust the position of the contact 24. The shaft 30 passes freely through and is supported by a sleeve 38 extending through the upper edge wall of the casing, said sleeve being externally threaded and held in the desired position by means of lock nuts as on opposite'sides of a flange 49 formed as part of the bracket 35. The threaded sleeve also serves to hold the dial H3 in position by means of a nut 4i integral with the dial.

The edge portion of the blanket where the thermostatic unit is to be located comprises separate plies 42 of blanket fabric as shown in Figs. 1 and 4. separability of the edges of these plies forthe length necessary to insert the thermostatic unit may suitably be provided by interrupting the edge stitching 43 or other means whereby these edges are normally united. For greater strength and resistance to wear, a pocket 44 of canvas or like material is inserted between the separable plies 42 to receive the unit. At the edge of the blanket, the pocket 44 has an open mouth the edges of which correspond with the separable edges of the blanket plies 52.

After the thermostatic unit has been inserted in the pocket, its mouth is closed and fastened to retain the unit, and the separable edges of the blanket plies are likewise closed and fastened.

center of the edge of the casing, as in the form shown herein, two sl de fasteners 45 are used, one

' extending from each end of the pocket inwardly to the. control dial I8. Preferably the edges of the pocket and of the blanket plies are cut out so as to fit closely around the oval dial as shown in Fig. 1.

The leads 4'! from the heating circuit extend into the pocket 44 through a suitable opening 48 in one end thereof and terminate in a connecting member 49 of any suitable type adapted to engage the terminals 3 and 4 of the thermostatic control unit to'connect it to the heating circuit.

It will be seen that the thermostatic control unit is housed and retained in the blanket as a unitary part thereof, eliminating the use of connecting cords and separate control units. The fiat thin shape of the unit and its arrangement substantially in the plane of the blanket prevent objectionable bulging of the blanket. At the same construction built to withstand wear and securelg closed and fastened to retain the thermostatic unit in place at all times.

It will be understood that the invention is not restricted to the embodiment illustrated in the drawings but is susceptible of various other'err rbodiments and changes in the form, details of construction, arrangement and location of the parts many of which will now occur to those skilled in the art. Hence reference should be had to the appended claims for a definition a:

the limits of the invention.

What is claimed is: g 1. In an electric blanket having wires enclosed in the blanket fabric and forming an electric heating circuit, a thermostatic control unit for controlling the current flowing in said circuit and having a manually settable control member, a pocket structure adapted to enclose said unit except for said control member, a portion of said blanket having two plies and said pocket structure being inserted between said plies andintegrally secured to the blanket fabric, the lead wires of said circuit extending from the interior of the blanket fabric into said pocket between the plies and without external exposure, a detachable connecting member located in said pocket and to which the ends ofsaid lead wires are connected, saidpocket having a mouth opening to] the exterior of the blanket for insertion of said unit therein and means for closing said mouth to secure said unit in said pocket between the plies with said control member protruding exteriorly of the blanket, and connecting means forming part of said unit and detachably connected with said connecting member inside said pocket.-

2. The combination defined in claim 1, said unit having a fiat relatively thin casing and said pocket structure holding said casing substantially in the plane of the blanket.

3. In an electric blanket having wires enclosed in the blanket fabric and forming an electric heating circuit, a thermostatic control unit for controlling the current flowing in said circuit and having a flat relatively thin casing and a mani'ially settable control member projecting therefrom,

means for holding said unit as part of saidblanket comprising a pocket structure adapted to house said un;t, said blanket at one part comprising separable plies and having an opening for insertion of said pocket and flat thin casing between the plies substantially in the plane of the blanket with said control member rotruding through said opening, said pocket having a mouth for insertion of said unit and the free edges of the blanket around said opening being secured to the Walls of said pocket adjacent said mouth, means for closing said mouth to retain said unit in said pocket, the lead wires of said circuit extending from the interior of the blanket fabric directly into said pocket, and a connecting member within the pocket connected to said leads and detachably connected to said unit.

4. In an electric blanket having two plies of blanket fabric with interposed wires forming an electric heating circuit, a thermostatic control unit for controlling the current flowing in said circuit and having a flat thin casing and a manually settable control member projecting from one edge thereof, 'a pocket of substantially the same size and shape as said casing and open along one edge for insertion of the unit therein with said control member projecting therefrom, said blanket plies being disconnected along one edge of the blanket for a distance substantially equal to the length of said pocket and the pocket being inserted between the plies, the disconnected edges of the blanket being secured to the open edges of the pocket, means for closing said open edges around said casing to retain said unit between the plies as part of the blanket, the circuit HAROLD F. SIVIITH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,312,830 Camm Aug. 12, 1919 1,921,343 Burkholder Aug. 8, 1933 2,048,880 Morgan July 28, 1936 2,162,021 Kidwell -June 13, 1939 2,215,042 Howard et al Sept. 17, 1940 

